Stabilization system for gunfire control apparatus and the like



Feb. 26, 1952 H. HARRIS, JR 2,586,817

STABILIZATION SYSTEM FOR GUNFIRE CONTROL. APPARATUS AND THE LIKE FiledNOV. 20, 1945 2 SHEETS--SHEET l T0 COM/ll TER L /L/Z Mmm.

Feb. 26, 1952 H. HARRIS, JR 2,586,817

STABILIZATION SYSTEM FOR GUNF'IRE CONTROL APPARATUS AND THE LIKE FiledNov. 2o, 1945 2 SHEETS- SHEET 2 .N .mvg

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Patented Feb. 26, 1952 STABILIZATION SYSTEM FOR GUNFIRE CONTROLAPPARATUS AND THE LIKE Herbert Harris, Jr., Cedarhurst, N. Y., assig'norto lhe Sperry Corporation, a corporation of Delaware ApplicationNovember 20, 1945, Serial No. 629,859

My invention particularly relates to a system adapted for use instabilizing re control apparatus such as gun sights and turrets mountedon aircraft. For the purposes of illustrating one adaptation of thisinvention, I will refer to a particular type of ordnance and to a gunturret mounted for stabilization on an aircraft. However, it is to beunderstood that this invention is not to be considered as limitedthereto, but may be applied to any type of apparatus or body which ismounted for stabilization about one or more axes in space.

Gun turrets, in accordance With present practices, are usually mountedon a craft, such as an airplane, for movement about ytwo mutuallyperpendicular axes of support, one thereof being termed the azimuthaxis, being normally vertical, and the other thereof being termed theelevation axis, being normally horizontal. Servomotors and associatedcontrol apparatus, which may be responsive to remotely positioned,manually operable handle bars, or, handle bars mounted Within theturret, are employed for driving the turret carrying the gun and sightin azimuth and also in elevation, or the turret in azimuth and the gunsand sight in elevation relative to the turret. In such installations,the gun sight is provided for the use of the operator in tracking atarget and suitable computing and gun control mechanisms are includedfor the purpose of offsetting the line of sight and the gun fortarget'interception purposes.

Heretofore, where such gun turrets are unstabilized, the handle bars ormanual controls function to operate control signal generators, forexample, potentiometers, one of which controls the azimuth servo and theother the elevation servo, the handle bars being movable in thedirections in which it is desired to drive the turret. The voltagederived from the potentiometers are respectively applied to suitableamplifiers which, in turn, control the direction and rate of operationof their associated servomotors. This control voltage ordinarilyfunctions to accelerate the servomotor until the speed thereof is suchthat the voltage output of a permanent magnet generator, driven by saidservo, bucks out the potentiometer voltage or modifies the originalsignal voltage, so that the rate of operation of the servo isproportional to the manually applied, initial signal. -In this manner,the servo will drive the turret at the established rate with respect tothe craft or plane but, of course, not necessarily so with respect tospace. If the plane has no angular movement about an axis parallelingthe axis Claims. (Cl. 318-489) about which the turret is driven, thenthe turret will be driven at a rate with respect to the plane and withrespect to space which is proportional to the potentiometer voltage, andthe voltage output of the permanent magnet generator will be a measureof the angular rate of the turret with respect to space or a truemeasure of the angular rate of a target. assuming that under theseconditions a target is being tracked by the use of the sight.

However, should the plane carrying the turret dive or roll, this motionof the craft will affect that motion of the turret which occurs aboutthe same or a parallel axis and as a result thereof, the turret opticsor sight will move olf the target and must be brought back thereon bymanipulating the hand-control. Assuming that under these conditions, theangular rate of the target remains a constant, the change in the voltageoutput from the potentiometer. because of movement of the hand-control,will change the turret rate. Therefore, since the angular rate of thetarget has not changed, the new turret rate, or the turret rate undertransient conditions of dive or roll as measured by the permanent magnetgenerator, Will be an erroneous measure of the target rate and not ameasure of the turret rate relative to space.

In the present invention, I propose to use a system of the generalcharacter of that above described which is adapted to control the ratesof a gun turret about its two axes of support, but, in connection witheach servomotor, instead of employing a permanent magnet generator orsimilar generator which is driven by the servo and provides a voltageoutput proportional to the speed thereof, I propose to provide a meansfor measuring the true rate of the turret about its axes of supportrelative to space, and to supply signals proportional to thismeasurement of true angular rate with respect to space which may besupplied to a computer, thereby providing correct and accurate inputdata, and which are also applied further to control the servos, wherebyto provide stabilization of the turret. In my proposed system, theangular rate at which the turret is driven about its axes of supportunder the control of the potentiometer voltage derived from the handlecontrols and the signal proportional to angular rate relative to spacemay vary with respect to the aircraft, but, will remain substantiallyconstant relative to space for a given setting of the handle controlsfor all movements of the aircraft in dive and roll. In other Words, theangular rate of the turret relative to space is dependent upon thesetting of the handle controis and will remain constant for a givensetting irrespective of movements of the craft in pitch. roll orazimuth.

It is, therefore, the primary object of the present invention to providea stabilizing system for a first body mounted for stabilization about anaxis of support on a second movable body or aircraft in which means areprovided for controlling the angular rate of the first body relative tothe second, a measurement of the angular rate of the first body relativeto space is taken, and the control exercised by said control means overthe angular rate of the first body is modified in accordance with themeasure of angular rate relative to space.

Another obiect resides in providing a stabilizing system of theforegoing character in which a gun sight or the like is stabilized,tending to remain on target during movements of tile craft in pitch androll; and in which true rates of the sight with respect to space areobtained, thereby providing a true measurement of the angular rate ofthe target which may be supplied as accurate input data to an associatedcomputing mechanism.

Still another object of the present invention resides in providing astabilizing system for a turret in which the initial control signalcontrols the rate of movement of the turret relative to the craft and asecond control signal, which is proportional to a measure of trueangular rate of the turret relative to space, is used to modify theinitial control signal, so that the turret rate with respect to space issubstantially a constant when no change in the initial signal occurs,and the movement of the turret in tracking a target is substantiallyunaffected by movements of the craft.

A still further object resides in-providing a stabilizing system inwhich an initial control signal, which may be manually adyusted orotherwise, directly controls a servo for driving the body or turret tobe stabilized while a gyroscope is caused to precess about an axisparalleling the axis about which said body is stabilized, so that thegyro follows the movements of the body or turret, and a signal derivedfrom the torque-exerting means, which causes precession of the gyro, isderived as a true measure of the angular rate of the body with respectto space and is used to modify the initial control signal so assubstantially to effect stabilization of the body thereby affordingaccurate control thereover by the initial signal.

The invention in another of its aspects relates to novel features of theinstrumentalities described herein for achieving the principal objectsof the invention and to novel principles employed in thoseinstrumentalities, whether or not these features and principles are usedfor the said principal objects or in the said eld.

A further object of the invention is to provide improved apparatus andinstrumentalities embodying novel features and principles, adapted foruse in realizing the above objects and also adapted for use inotherfields.

With the foregoing and other objects in view, my invention includes thenovel method and the novel combinations and arrangements of elementsdescribed below and illustrated in the accompanying drawing, in which-Fig. 1 schematically illustrates the system of the present invention asapplied to the control of a turret or other object about a single axisof support;

Fig. 2 schematically represents the system of the present invention asapplied to a gun turret for stabilizing it about its two axes ofsupport;

Fig. 3 is a fragmentary perspective view of a gun turret and sighttherewithin mounted for stabilization in accordance with the presentinvention about mutually perpendicular axes on a craft; and

Fig. 4 schematically shows a modified manner in which to derive signalsproportional to precession rates of a gyro.

In the drawings, I have shown a gyroscope as the means which normallyprovides a substantially :dxed reference with respect to space but whichmay be caused to move or precess at an angular rate corresponding to therate at which the turret or other obJect is rotated by the servomotor.

In Fig. 1 of the drawings, I have shown one embodiment of my inventionwherein a gyroscope is arranged to stabilize and provide an accuratemeasurement of the rate of rotation of the turret about one of its axesof support relative to space, while in Fig. 2, a system is shown forcomplete stabilization of the turret by means of a single gyroscopewhich also functions to provide accurate measurements of rates ofoperation of the turret relative to space about both of its axes ofsupport.

Referring first to Fig. 1, 1 indicates generally the schematicallyillustrated turret, mounted for movements in elevation about an axis 2and for rotation in azimuth about an axis 3. In the schematicillustration, the turret I is supported on trunnions 4 in a gimbal ring5 which in turn vis mounted on trunnions 6 to rotate in bearings 1lwhich, it will be understood, are mounted on the airplane or othercraft carrying the turret.

A servomotor 8, which may be of any suitable conventional design andwhich may be of the character of those more particularly shown in Fig.2, is arranged through its output shaft 9 and associated gearing I0 todrive the turret I in azimuth about the axis 3. A manual control such asthe handle bars illustrated in Fig. 2, and indicated at II, enables theoperator or gunner to control a potentiometer I2 comprising theresistance element I3 and the wiper arm I4 operated by the handlecontrol II. A battery I5 or other suitable source of voltage isconnected across the potentiometer winding I3 and a midtap on thepotentiometer winding is connected through lead I6 to the amplifier I1,while the arm or wiper I4 is connected through lead I8 to the amplifier.

The amplifier functions to supply an output voltage which isproportional to the signal voltage derived from the potentiometer andthe output of the amplifier reverses in polarity, or in phase sense ifthe servomotor is of an alternating current type, upon reversal of thepolarity of the signal Voltage supplied thereto. The signal voltagederivedfrom the handle bar control may be of an alternating character,if desired. The signal voltage derived from potentiometer I2 constitutesthe initial or primary signal controlling the rate and direction ofoperation of the servomotor and, hence, in view of the additionalvoltage signal derived from the gyroscope as hereinafter described, therate of the turret I about axis 3 will be dependent upon the setting ofthe handle bar control II relative to the aircraft on which the turretis mounted.

In accordance with my invention and in lieu of the feedback signalvoltage from a permanent magnet generator which is proportional to speedof rotation of the servomotor, I supply a feedback voltage which isproportional to rate of turn or precession of a gyroscope which iscaused automatically to precess at the rate of turn of the turretestablished by the handle bar controls.

In the embodiment illustrated in Fig. 1, a gyro indicated generally atI9 is mounted within the t1 'et and is free to precess about the axis 20thereof which preferably parallels the axis of supports 3 of the turret.The gyroscope may be of a conventional character including a gyro rotorcase 2| within which the rotor is mounted to rotate about the spin axis22. The rotor case 2| in turn is supported on trunnions 23 in the gimbalring 24. Gimbal ring 24 is in turn supported on trun nions 25 to rotatein suitable bearings 26 (oni,y one of which is shown) about the axis 2U.It will be understood, although' otherwise shown for clearness inillustration, that the gyro and its bearings 26 are mounted within theturret I.

In order to cause the gyro to precess about its axis 20 at the same ratethat the turret is caused to rotate about its axis 3, I haveschematically shown a pick-off or signal voltage generator ar-V rangedto control the precession of the gyro in accordance with movements ofthe turret. In the embodiment illustrated, I have shown an E-type signaltransformer or generator indicated generally at 21. This signaltransformer is of a wellknown type comprising an E-shaped core 28 whichin the embodiment illustrated is mounted to move with the gyro or gimbalring 24 thereof about the axis 20, and an armature 29 which is rotatedabout the axis 20 of the gyro and in timed relation with rotation of theturret about the axis 3. This may be accomplished as schematically shownby means of bevel gears 30, one of which is keyed to rotate through theoutput shaft 9 of the servomotor and the other of which is connectedthrough shaft 3| with the armature 29 of the signal transformer.

It will be understood that the core and armature of the transformer 21are formed of suitable magnetic material and that the core carries anexciting winding on the middle leg thereof and a pickup winding on eachend leg. The exciting winding, which is not illustrated but isschematically represented as connected with a suitable source ofalternating current 32, functions to pass equal amounts of ux throughthe end legs thereof when the armature is so positioned as to providetwo balanced parallel magnetic circuits. When the armature moves fromthis position in one direction or the other, the voltages induced in thepickup windings, which are not illustrated but are connected in seriesacross the leads 33 and 34, provide a resultant voltage output havingone phase sense when the armature moves relative to the core in onedirection and of the opposite phase sense when this motion is reversedfrom the zero voltage output position of he armature. To accomplish thisresult, of course, the two pickup windings are connected in voltagebucking relation.

Leads 33 and 34 are connected to a suitable amplifier 35 which ispreferably of a phase-sensitive nature when a transformer of thecharacter of il at indicated at 21 is employed to provide a reversiblephase alternating voltage signal input thereto. The amplifier isconnected with a suitable source of alternating reference voltage 32awhich is preferably the same source as source 32, above referred to, forthe signal transformer 21. The amplifier preferably functions, at leastin the embodiment herein illustrated, to provide a direct current outputdifferentially to control a torque motor indicated generally at 38. Forillustration purposes, I have shown in Fig. 1 the output stage of theamplifier as including the electron tubes 31 and4 38 connectedrespectively in the two parallel channels of the amplifier and havingplates or anodes connected through the differential eld windings 39 and40 of torque motor 36. A mid-tap between these windings constitutes acommon return to the amplifier as shown, tube 31 serving to control thecurrent in winding 39 and tube 38 similarly serving to control thecurrent in winding 40. The amplifier may be adjusted so that when nosignal is supplied thereto, the currents in the windings 39 and 40 areequal and opposite and, therefore. no torque output is derived fromtorque motor 36. When, however, a signal voltage of one phase sense orthe other is supplied to amplifier 35, the current in winding 39 or 40predominates over the other, depending upon the phase sense of thesignal, therefore, producing a torque output from motor 36 in such adirection as to cause the gimbal ring 24 of the gyroscope to precess inthe same direction and at the same rate as that at which the armature 29of the signal transformer is rotated by the servomotor.

It will be understood that the torque applied about the axis oftrunnions 23 of the gyro will cause precession of the gimbal ring aboutaxis 20 of the gyro and that the rate with respect to space of thisprecession will be proportional to the torque so applied. Furthermore,the resultant current or the difference between the currents flowing inthe eld windings 39 and 40 of the torque motor will be a measure of thetorque exerted by the torque motor or a measure of the rate ofprecession of the gyroscope. In the embodiment shown in Fig. 1, and forpurposes of illustrating one manner in which this torque may bemeasured, I have shown the cathode circuits of the tubes 31 and 38 asincluding resistors 4| and 42, and I have also shown a battery 43 as asource of plate potential. Hence, the currents iiowing in the platecircuits of tubes 31 and 38 will produce a differential voltage dropacross resistors 4| and 42 and the resultant or net voltage drop betweenthe cathodes of these tubes or across the resistors 4| and 42 will be ameasure of the torque applied to the gyro and the rate of precessionthereof. Hence, leads 44 are connected to the cathode ends of theresistors 4| and 42, so that a signal voltage will be developedthereacross which is proportional to the rate of precession of gyroscope|9.

Leads 44 may be connected, as indicated, to a computer to supply theretoa signal voltage which, as hereinafter more particularly pointed out, isan accurate measure of the angular rate of turret about axis 3 andrelative to space. In accordance with this invention, leads 44 are inturn connected to leads 45 to the amplier I1 and, by means of leads 45,the signal voltage across leads 44 is supplied to amplifier |1 inbucking relationship to the signal supplied thereto from thepotentiometer I2.

The operation of the embodiment of my invention shown in Fig. 1 is asfollows: First, let us assume that the aircraft on which turret ismounted has no angular movement relative to space, and let us furtherassume for description purposes that the sight, handle control andoperator are within the turret. In order to track a chosen target, vthatis, maintain theline Iof sight of the turret optics on the target whilethe target moves relative to the aircraft, theoperator manipulates thehandle bars or manual controlsA to supply a signal voltage outputv frompotentiometer I2. The potentiometer I2 may be considered as the sourceof a first or primary signal voltage or the initial signal employed incontrolling the servo, and the polarity thereof is dependent upon thedirection in which the handle controls are turned. This initial signalfunctions to cause the servomotor to drive theturret about its axis 3 inthe desired direction to track the target .At the same time, thearmature 29 of signal transformer 21 moves relative to the core 28thereof and supplies a signal voltage to the amplifier 35, the outputsof the amplifier Vbeing such asY to apply a torque on the gyro by meansof the torque motor 36 which will cause it to precess in the samedirection in which the armature 29 is moved and at the same rate. Inother words, the gyro is caused to precess about its axis 20 whichparallels the axis 3 of the turret and to follow the turret in itsrotation thereabout.

The rate signal derived across the cathode resistors 4I and 42, which isa measure of the angular rate of precession of gyroscope I9, is suppliedin bucking relation to amplifier I1. It is assumed for purposes ofillustration that the servomotor herein employed is of the Vickershydraulic type, wherein the control signals so control the servo that itwill continue to operate at a rate proportional to the setting of thehandle controls II when the signal voltage derived therefrom is reducedto zero by the rate signal fed back from the torque motor controlcircuit. This type of servo is Well known in the art and a detaileddescription thereof is not believed necessary but reference may be madeto U. S. Patents Nos.'2,l77,098, issued to T. B. Doe, et al., and2,189,823, issued to H. P. Vickers et al. Obviously, other types ofservos may be employed wherein the difference between the initialcontrol signal such as that derived from the potentiometer I2 .and thefeedback rate signal such as that derived from the torque motor circuitis of such value as to drive the servo at the desired rate or at a rateproportional to the handle bar setting.

Therefore, assuming that the handle bar control II is moved to somepredetermined position, the repeat-back signal voltage will, in the typeof servo system herein assumed, equal and oppose the signal derived frompotentiometer I2, reducing the resultant signal voltage supplied toamplifier I1 to zero, and servomotor 8 will drive the turret I at a rateproportional to the handle bar setting. Since the gyroscope precesses atthe same rate as the turret and at the same rate at which the line ofsight is angularly moved, so long as the line of sight remains on thetarget, the gyroscope will provide an accurate measure of the angularrate of the target in space.

If, during this operation with the handle bar control set, the aircraftshould rotate about lthe axis 3 or 20, it would be necessary for theoperator to readjust the setting of the handle controls because of theadded movement of the craft if the gyroscope and its associatedrepeat-back circuit were not employed. However. the gyroscope will tendto maintain its position in space and, therefore, the rate signal whichis derived from the torque motor circuit will normally control theservomotor in such a manner that angular movement of the turret aboutits axis 3 will be synchronized with angular movement of the gyro aboutits axis 20. Hence, the repeat-back of the ratesignal functions tostabilize the turret under the control of the gyro and to maintain therate of the turrent relative to space as prescribed by rate` dependentupon the setting of the handle control, but at a diierent rate relativeto the craft. Therefore, the repeat-back signal derived from the controlfor the torque motor of the gyroscope will tend to maintain the line ofsight on the target, even though movement of the craft about the same orparallel axis occurs, so that it is unnecessary for the operator toadjust the handle'bar setting except to maintain the desired rate of thesight or turret as though no movement of the craft had occurred.

In Fig. 2, I have schematically shown my invention as applied to thestabilization or control of the gun turret about two of its mutuallyperpendicular axes of support, as clearly illustrated in Fig. 3.Referring first to Fig. 2, the manually operable handle bars 46 aremovable by the operator about the azimuth axis 41 and also about theelevation axis 48. In the embodiment illustrated, the handle barstogether with the gyroscope are mounted within the turret indicatedgenerally at 49 in Fig. 3. Movement of the handle bars about the azimuthaxis 41 serves to rotate the wiper arm 50 of the potentiometer 5I whichmay be generally similar to potentiometer I2, hereinbefore described;and which is employed to provide a signal voltage for controlling theazimuth servo.

Operation of the potentiometer 5I may be .accomplished through themedium of gears 52, one of which is secured on the shaft of the wiperarm and the other of which is directly coupled with the handle bars 46.Similarly, a second potentiometer indicated generally at 53 is connectedfor operation by the handle bars when they are moved about the elevationaxis 48. The wiper arm 54 of potentiometer 53 is secured to shaft 55which is driven by gear 5B which, in turn, is operated by cylindricalrack 51. Rotation of handle bars 46 about axis 48 produces axialtranslation of rack 51 through the medium of gear 58, meshing withcylindrical rack 59. Hence, movement of handle bars 46 about axis 41produces a corresponding movement of wiper 50 over the resistanceelement of potentiometer 5I and rotation of handle bars 46 about axis 4Bproduces a corresponding rotation of wiper 54 over the resistanceelement of potentiometer 53. Potentiometer 53 is employed to provide asignal for controlling the elevation servo. Each of the resistanceelements of potentiometers 5I and 53 is connected across a suitablesource of current such as battery 60 and a center tap on each resistanceelement together with the wiper arm of each potentiometer arerespectively connected to output leads 6I and 62, leads 6I beingconnected with the azimuth servo amplifier 63 for controlling theazimuth 9 servo, and leads 62 being connected to the eleva tion servoamplifier 64 for controlling the elevation servo.

The azimuth and elevation servomotors are re- Vspectively initiallycontrolled by the handle bars 46 in response to signal voltages derivedfrom the potentiometers and 53, substantially in the same manner as theservomotor 8 hereinbefore described in connection with Fig. 1.

In the embodiment of my invention shown in Fig. 2, I employ a singlegyroscope for measuring the angular rates of the turret about its twoaxes of support on the craft. For example, as shown in Fig. 3, theturret 49 is supported on trunnions 65 for movements in elevation aboutthe axis 66 and relative to the yoke or gimbal ring 61. Ring 61 in turnis supported to rotate in azimuth about the azimuth axis 6B by means ofsuitable trunnions 69 or the like, journalled in suitable bearings inparts of the craft structure, such as the bearing support 10 illustratedin the upper por-r tion of Fig. 3 and the bearing supports 'H appearingat the bottom of Fig. 3. The gyroscope indicated generally at 12 in Fig.2 is mounted for movement about the axes 13 and 14. These axes are, inaccordance with the invention, disposed in parallel relation to the axesof support 66 and 68 of the turret. In other words, axis 13 parallelsthe turret axis 66 and axis 14 of the gyroscope parallels the turretaxis 68.

'I'he spin axis 15, of the gyroscope may, therefore, parallel the lineof sight provided by the optical system represented generally at 16 inFig. 3. The rotor bearing case 11 of the gyro is mounted on trunnions10, aligned with the axis 14, and supporting the rotor case in gimbalring 19. The gimbal ring 19, in turn, is supported on trunnions 80 insupports 8| whichI are fixed to the casing of the instrument, trunnions80 being aligned with the axis 13 of the gyroscope. In order to affordfree movement of the gyroscope about both of these axes and at the sametime to operate signal generators or pick-offs for detecting suchmovements of the gyroscope, the rotor bearing case is connected throughstem 82 with a yoke 83 mounted to rotate about an axis normallycoincident with the axis 14 of the gyro. In this manner, rotation of therotor case of the gyro about the axis 14 will be imparted to the yoke 03and will serve to move the armature 84 of an E-tyne transformer orpick-01T 85 relative to the core 86 thereof, which core is mounted inxed relation to the casing of the instrument. The stem 82 is movablewithin a slot 81 in the yoke 83 which is of a length suilicient topermit the necessary movement of the gyro casing and gimbal ring 19about the axis 13. The trunnion 80 is arranged to operate the armature88 of a second pick-01T or signal transformer 89, the core 90 of whichis mounted in fixed relation to the casing of the instrument. Since thecasing of the instrument .is xed within the turret. pickoffs 85 and 89will detect movements of the turret relative to the gyroscope and viceversa.

It is herein assumed that axis 14 of the gyroscope parallels the azimuthaxis of the turret and therefore when the handle bar controls 46 areoperated to cause the turret to rotate in azimuth at a prescribed raterelative to the craft, the casing of the gyroscope will move the core 86of pick-off 85 relative to the armature 84. As a result thereof, asignal voltage output will be supplied across the leads 9| supplying analternating signal voltage to amplifier 92. functions in the same manneras amplifier 35 This amplier.

hereinbefore describedin connection with Fig. 1 to control torque motor93 which is mounted on trunnion to exert a torque about the axis ,13 andthereby cause the gyro to precess in the same direction as the casingthereof or in which the core 96 of the pick-off had been turned relativethereto. Leads'94 serve to connect the output of amplifier 92 with thetorque motor 93. and it will be understood that the torque exertedthereby will be suiiicient to cause the gyroscope to precess about theaxis 14 at the same rate as that at which the azimuth servo drives theturret as hereinbefore described.

'I'he signal voltage, which is proportional to rate of precession of thegyro, and which is derived from the output of the torque motor amplier92, as described in connection with the ampliiler 35 in Fig. 1, is fedback to servo amplifier 63 by leads 95 and this signal may also besupplied through leads 96 as accurate rate input data to a computer asindicated.

In the embodiment of my invention herein illustrated, the azimuthservomotor is indicated generally at 91 and comprises an A end orvariable displacement pump 98 which is driven by preferably a constantspeed motor 99. The fluid or oil pumped from the A end is deliveredthrough one of the pipes |00 and returned through the other to and froma hydraulic motor |0|, termed the B end. The displacement of the pump orA end 98 is controlled by a lever |02 which is positioned by the pistonin a stroke cylinder |03. As is well known in the hydraulic servomotorart, the lever |02 controls the displacement within the pump 98 and boththe rate and direction of operation of the B-end. Therefore, theposition of the piston within the stroke cylinder |03 is determinativeof the direction of rotation of the azimuth servo. Control valve |04serves to control the admission and exhaust of oil or other fluid to theinterior of the stroke cylinder |03 and to produce movement of saidpiston in either direction depending upon the direction of movement ofthe valve member within the valve |04 which is actuated by torque motor|05 which, in turn, is controlled by the output of amnlier 63. In brief,through the above-described servo system components, the azimuth servo inl will drive the turret in azimuth about its axis 68 in a direction andat a rate dependent upon the two signals derived from the potentiometer5| and the amnlier controlling the toroue motor 93 of the gyroscope ashereinbefore described in connection with Fig. 1. In Figs. 2 and 3, Ihave schematically represented the azimuth servo |0| as driving theturret through the medium of internal ring gear |06 and pinion |01. Theinternal gear may be secured to the craft and in this case, as shown,the servo moves with the turret.

As hereinbefore indicated, I have herein illustrated the servomotors asof the Vickers hydraulic type wherein the rate of the servo output isproportional to the signal derived from the control handlepotentiometers when this signal is bucked out by a signal proportionalto the speed of the servo. Obviously, other types of servos may beemployed with the rates thereof dependent upon the signals derived bothfrom manual controls and a gyroscopic follow-up system of the characterherein described.

The system embodiying the gyroscope 12. handle bars 46 and the elevationservomotor indicated generally at |08 is substantially the same as abovedescribed in connection with the azimuth servo. Briefly, a ring gear |09or a gear segment as shown may be secured to the turretv in concentricrelation to the elevation axis 66.`

In this case, the B-end of the servomotor is mounted on the yoke orgimbal ring 61 to control elevation movements of the turret or gunrelative to the gimbal ring. The A-end of servomotor |08 is controlledby the piston within stroke cylinder I2 and the position of said pistonis controlled by the valve ||3, in turn. actuated by the torque motorIll. The torque motor ||4 is controlled by the output of the elevationampller 64 to which an initial control signal voltage is supplied fromthe potentiometer 53 associated with the handle bars 46 and the leads62. 'I'he pick-off 89 for detecting relative movement between thegyroscope and turret about the axis I3 of the gyro supplies a controlsignal voltage to amplier ||5 which is similar to ampliers 35 and 92hereinabove described and the output thereof is supplied to control atorque motor IIS or the rate of precession of the gyro about axis 13. Asignal voltage proportional to the torque 'applied or rate of precessionof the gyro about axis 'I3 is supplied thro-ugh leads I I'I to theelevation servo amplifier 66 and through leads I I8 to a suitablecomputing mechanism.

The ampliers 63, 64, 92 and I I5 are preferably phase-sensitiveamplifiers in view of the nature of the alternating voltage signalssupplied thereto, and are preferably all connected to the same source ofalternating reference voltage, indicated at I I9, from which the signaltransformers are excited.

The elevation servomotor functions like the azimuth servomotor to drivethe turret in elevation about its axis of support 6B at a rate dependentupon the setting of the wiper of potentiometer 53, and also under thecontrol of the signal voltage derived from the torque motor amplifler||5. With this arrangement and assuming that the spin axis of the gyroparallels the line of sight from the optics into space, the gyroscopewill precess about its axes I3 and 'I4 in accordance with movements ofthe turret about the axes 66 and 68 substantially to maintainparallelism between the line of sight and the spin axis of the gyro. Thecomputing mechanism, of course, offsets the bore axis of the gunrelative to the line of sight for target interception purposes.

It should be evident from the above descrip- .tion of the system shownin Fig. 2 that the single gyro 'I0 will function to provide true andaccurate measurements of the angular rates of the turret or the line ofsight relative to space, and about the axes of support 66 and B8.Likewise, the gyroscope 12 functions to maintain or to tend to maintainthe line of sight upon a target while being tracked and during roll,pitch and like movements of the craft so that the rate of movement ofthe sight relative to space is substantially unaffected by thesemovements of the craft and the gunner or operator has no greater problemin keeping his sights on the target than he would have if the systemwere mounted on a stationary support.

In Fig. 4, I have schematically shown an alternative construction forderiving signals proportional to rates of precession of a gyroscopewherein a rate gyro, indicated generally at |20, is employed. Inconventional manner, this gyro is spring constrained about its axis ofprecession dened by trunnions |2| which are, of course, journalled insuitable bearings (not shown).

The tension of spring |22 may be adjusted by knob |23 to control themagnitude oi.' precession The spin or angular rotation of gimbal ring|24. axis of the gyro rotor is indicated at |25 and the axis about whichthe angular rate is measured is indicated at |26.

A gyro of this character will precess or turn about the axis oftrunnions |2| an angular distance proportional to the rate of turnthereof about axis |26. This angular displacement may be measured by anelectrical pick-off or signal generator or by any other type of pick-oftwhether electrical or otherwise to supply a signal proportional to saidangular displacement of the gimbal ring from its initial, springconstrained position.

In the present case, I have illustrated an induction type pick-off orsignal generator |21 having a fixed stator winding |28 energized from asuitable source of alternating current and a rotor winding |29 which ismounted on or rotated by trunnion |2|. This pick-oil may be wound toprovide a linear output. potentiometer, for example, may be used tosupply alternating or unidirection signal voltage outputs.

When using-a rate gyro to supply a signal output proportional to rate ofturn in the present invention, one thereof is mounted to turn with theturret or sight and with the axis |26 thereof coincident or parallelwith the axis 68 of the turret mounting shown in Fig. 3, and a secondrate gyro is likewise mounted to turn with the turret or sight but withthe axis |26 thereof coincident with or paralleling the axis 66 of theturret mounting or sight shown in Fig. 3. Hence. the signal output ofone rate gyro unit will constitute a measure of turret rate in azimuthrelative to space while that of the other rate gyro unit will constitutea measure of turret and/or sight rate in elevation relative to space.These rate signals may be used as hereinabove described to control therespective servomotors and effect substantial stabilization of theturret and sight and also as input data to the associated computingmechanism.

Advantages of the present system are as follows: f

1. The angular rates of a target are accurately and correctly measuredwith respect to space as above described.

2. The line of sight is stabilized in that it tends to remain on thetarget during dive, roll or other angular movements of the craft.

3. Errors in measuring rate due to the bearingsand friction of thegimbal rings of the gyroscope are substantially eliminated because at aconstant rate of turn of the turret, the gyroscope which is mountedtherein turns at substantially the same rate.

4. Any instability which may otherwise be caused by-gmbal lock iseliminated because the gyro follows the line of sight or turret.

5. Additionally, a single gyro may be employed. and in View of thenature of its use a comparatively small gyro is sufficient.

Although in the foregoing I have illustrated and described the manuallyoperable control as a means for deriving an initial or primary controlsignal to which the servos are primarily responsive, it will beunderstood ,that other means for supplying such a signal, such as radarsystems for automatic target tracking purposes, may be used to supplythe primary control sig- On the other hand, a

nal, are contemplated as within the broad scope of the presentinvention.

While I have described my invention in its preferred embodiments, it isto be understood that the words which I have used are words ofdescription rather than of limitation and that changes within thepurview of the appended claims may be made without departing from thetrue scope and spirit of my invention in its broader aspects.

What is claimed is:

1. In a stabilizing system for a rst body mounted for'stabilizationabout an axis of support on a second movable body, a servomotor forturning said rst body about said axis, a source of iirst control signaland an amplifier responsive thereto for controlling said servomotor, agyroscope, means for causing said gyroscope to precess at a ratecorresponding to the rate of turn of said first body, means for derivinga second signal proportional to the rate of precession of saidgyroscope, and means for applying said second signal to said amplifierin bucking relation to said first signal.

2. In a stabilizing system for a first body mounted for stabilizationabout an axis of support on a second movable body, a source of firstsignal, an amplier responsive to said signal and a servomotor controlledby said amplifier for turning said body about said axis, said servomotorbeing so constructed and arranged as to drive said first body relativeto said second body at a rate proportional to the magnitude of thesignal supplied by said amplifier and at a constant rate when the signalsupplied by said amplifier is reduced to zero, a gyroscope, means forcausing said gyroscope to precess at a rate corresponding to the rate ofturn of said rst body, means for deriving a signal proportional to therate of precession of said gyroscope, and means for supplying said lastrecited signal to said amplifier in bucking relationship to said rstsignal.

3. In a stabilizing system for a first body mounted for stabilizationabout an axis of support on a second movable body, driving means forturning said rst body about said axis, control means for said drivingmeans, a gyroscope free to turn about an axis parallel to the axis ofsupport of said first body, means for applying a precessing torque tosaid gyroscope, signal generating means responsive to relative movementbetween said first body and said gyroscope for controlling saidgyro-precessing means whereby to cause said gyroscope to follow saidfirst body and to precess at a rate corresponding to the rate of turn ofsaid first body, means for deriving a signal from said gyro-precessingmeans proportional to the rate of precession of said gyro, and meansresponsive to said signal for further controlling said driving means.

4. In a system for determining the rate of movement with respect tospace of a body mounted to turn about an axis of support on a secondbody movable in space, a gyroscope free to move about an axisparalleling said axis of support, means for deriving a signalproportional to relative displacement between said body and saidgyroscope, torque-producing means responsive to said signal forprecessing said gyroscope at a rate corresponding to the rate of turn ofsaid body, and means for deriving from said torque-producing means asignal proportional to the rate of precession of said gyroscope.

5. In a system for determining the rate of movement with respect tospace of a first body carried on a second body and movable about an axisrelative thereto, driving means for turning said first body about saidaxis relative to said second body, a source of first control signal,control means responsive to said first signal and to a second signal forcontrolling said driving means, a gyroscope free to precess about anaxis paralleling said first-mentioned axis, means for precessing saidgyroscope at a rate corresponding to the rate of turn of said firstbody, means for deriving a second signal proportional to the rate ofprecession of said gyroscope, and means for further controlling saiddriving means by said second signal whereby said first body will rotateat a constant rate with respect to space when said first control signalis unaltered.

HERBERT HARRIS, JR.

REFERENCES CITED The following references are of record in th flle 0fthis patent:

UNITED STATES PATENTS Date l Germany Aug. 1,1935

